As disclosed in German patent document DE 33 42 749 A1 a plate-type reactor for chemical syntheses under high pressure is known wherein the plates take the form of flat right parallelepipeds which are bounded by sheet-metal walls and which each form a chamber filled with a catalyst, the two largest walls of which are gas-impermeable. Flow of the reaction gases through the granular catalyst takes place either horizontally or vertically through two open or pierced narrow sides of the right parallelepiped which are located opposite each other.
With a view to heating or cooling the reactor (depending on the reaction, either exothermic or endothermic), cooling channels are provided in the chambers for the circulation of a liquid heat-exchange. These cooling channels may be formed by sheet-metal structures which take the form of crosspieces, corrugated sheet metal or such like and which are firmly connected to the smooth walls, for example by welding. The totality of the chambers is adapted in outline to the shape of a cylindrical reactor, so that the chambers have, in part, varying sizes and are perfused in succession by the reaction gases, e.g. also in groups. The structural design is enormously elaborate, and the production output, which as such is already low, can at best be increased by axial lengthening and/or by a parallel connection of several reactors.
EP 0 691 701 A1 disclose a stacked reforming generator wherein, with a view to carrying out endothermic reactions, a reforming chamber with heat-recovery medium connected downstream is embedded in each instance between two combustion chambers. In this case the directions of flow of the gases in the reforming chambers and in the combustion chambers are opposite, semipermeable walls being arranged ahead of the heat-recovery chambers which are connected downstream in each instance. The heat-recovery medium is in the form of spheres of aluminum oxide, for example. With a view to improving the exchange of heat, between the individual chambers there are arranged horizontal heat-conducting sheets which are provided with openings for the passage of fuel in the heating region. Between each such group of three there is located, in turn, a fuel-distributing chamber. The device is extraordinarily complicated in structure and is neither provided nor suitable for exothermic processes since the device possesses no cooling channels, as this would run counter to the sense and purpose of the known art. The structural design, which is not suitable for operation at high pressure, serves the purpose of shortening the overall length by virtue of the omission of special heating zones.
Another development is disclosed in DE 44 44 364 C2; namely, a vertical fixed-bed reactor with rectangular casing cross-section for exothermic reactions between gases, wherein the fixed bed of catalysts is subdivided by vertical partitions for the purpose of forming separate flow channels and a plate-type heat-exchanger. Below and above the flow channels, catalyst-free interspaces are located in each instance in alternating arrangement. The gases emerge at the upper end of the fixed bed from some of the flow channels and are conducted again through lateral overflow channels beneath the fixed bed, from where they are supplied through the respective other flow channels to a gas outlet nozzle. The device is neither provided nor suitable for endothermic processes, since the device possesses no means for a supply of heat. In addition, on account of the rectangular cross-section of the casing the structural design is not suitable for operation at high pressure.
Disclosed in EP 0 754 492 A2 is a plate-type reactor for reactions of fluid media which is constructed in the form of a static mixer with exchange of heat. For this purpose, numerous plates are stacked on top of one another, the lowest of which is closed in the outward direction and the uppermost of which merely possesses bores in the outward direction for the intake and discharge of the media to be caused to react or that have been caused to react and of a heat-exchange medium. The respective second plates from below and from above possess, in addition, recesses which are open on one side for the redirection of the reactants through the stack in a meandering shape. In the plates situated in between there are located X-shaped or cloverleaf-shaped mixing chambers and reaction chambers which are connected to one another in the direction of the stack. The heat-exchanger channel is also guided through the stack of plates in a meandering shape. The plates consist of material with good thermal conductivity, preferably metals and alloys, have a thickness between 0.25 and 25 mm and can be produced by micromachining, etching, stamping, lithographic processes etc. They are firmly and tightly connected to one another on their surfaces outside the apertures, i.e. on the periphery, for example by clamping, bolts, rivets, soldering, adhesive bonding etc., and thereby form a laminate. The complicated flow paths give rise to high resistances to fluid flow and are not capable of being filled with catalysts. On account of the requisite machining, the production process is extremely elaborate, because all the contact surfaces have to be finely ground.
In DE 197 54 185 C1 there is shown a reactor for the catalytic conversion of fluid reaction media wherein a fixed bed consisting of catalyst material which is supported on a sieve plate is subdivided by vertical thermal sheets which each consist of two metal sheets which have been deformed repeatedly in the shape of a cushion and which are welded to one another, including a space for conducting a cooling or heating medium through at points which are distributed in the form of a grid. The reaction media and a heat-exchange medium are conducted in counterflow through the columns of the fixed bed between the thermal sheets, on the one hand, and the cavities in the thermal sheets, on the other hand. The container of the reactor is constructed in the form of a vertical cylinder, and the thermal sheets are adapted to the cylinder, that is to say they have varying sizes. Also in this case the production output can at best be increased by axial lengthening and/or by a parallel connection of several reactors.
DE 198 16 296 A1 from the same applicant shows that it is known to generate an aqueous solution of hydrogen peroxide from water, hydrogen and oxygen in a reactor which may contain both a fixed-bed packing consisting of particulate catalysts and planar monolithic carriers which are provided with channels, take the form of heat-exchangers and are provided with coatings of catalyst material. By way of catalysts, elements from the 8th and/or 1st subgroups of the Periodic Table of Elements are specified, such as Ru, Rh, Pd, Ir, Pt and Au, whereby Pd and Pt are particularly preferred. Activated carbon, water-insoluble oxides, mixed oxides, sulfates, phosphates and silicates of alkaline-earth metals, Al, Si, Sn and of metals pertaining to the 3rd to 6th subgroups are specified by way of carrier materials. Oxides of silicon, of aluminum, of tin, of titanium, of zirconium, of niobium and of tantalum as well as barium sulfate are specified as being preferred. Metallic or ceramic walls having the function of heat-exchangers analogous to plate-type heat-exchangers are named as materials for monolithic carriers. The specified experimental reactor had an inside diameter of 18 mm with a length of 400 mm. The temperatures were within the range from 0 to 90° C., preferably 20 to 70° C., the pressures were between atmospheric pressure and about 10 MPa, preferably between about 0.5 and 5 MPa. Also with respect to this state of the art, the production output can at best be increased by axial lengthening and/or by a parallel connection of several reactors.
The reactors shown in DE 195 44 985 C1 as well as DE 197 53 720 A1 comprise a plate-like heat exchanger wherein the fluid heat-exchange medium is conducted through the slot formed between two plates. There is no hint on the function of width slot-shaped reaction spaces.
Further, there is disclosed a device in DE 197 41 645 A1 which comprises a microreactor with reactions and cooling channels wherein the depth “a” of the reaction channels is<1000 μm and the smallest wall thickness “b” between reaction and cooling channels is<1000 μm. This document gives no indication to use reaction spaces other than said channels. A microreactor comprising many parallel grooves as reaction spaces is taught by DE 197 48 481. The manufacture of a reactor for large scale throughput is expensive.
Furthermore, so-called microreactors are known in which the dimensions of the flow channels are in the region of a few hundred micrometres (as a rule, <100 μm). This results in high transport values (heat-transfer and mass-transfer parameters). The very small channels act as flame barriers, so that no explosions are able to spread. In the case of toxic reactants, a small storage volume (hold-up volume) leads, in addition, to inherently safe reactors. But a filling of the channels with catalysts is impossible by reason of the small dimensions. A further crucial disadvantage is the elaborate production process. In order to avoid clogging of the very small channels, over and above this an appropriate protection of the filter has to be provided for upstream of the reactor. High production outputs can only be obtained by means of parallel connections of many such reactors. Furthermore, the reactors can only be operated at higher pressures when the cooling medium is at the same pressure level.